[Hallicrafters] Replacing rect tubes with diodes question

[Kenneth G. Gordon]

On 13 Feb 2008 at 8:48, WØQFC wrote:

> I want to replace the # 80 in my S-40A with diodes so I can reduce
> heat by less draw on the tranny.

Can be a good idea if done correctly. You will reduce the 
tranny heat by about 10 watts.

> Can I just use two diodes that will handle the current,

and voltage,

> or is there
> something else I should do ~ additional parts, etc?

You should include a resistor in series at the input of each 
diode, or at the output of the two, to maintain the output 
voltage at the correct voltage. Diodes have far less forward 
voltage drop than a tube-type rectifier, and if you simply 
replace the tube with a pair of diodes the output voltage will 
be too high, especially since modern line voltages are higher 
than when the receiver was built.

You MAY have to bypass each diode with a .001 mfd disk 
ceramic since, in my, and others', experience the diodes can 
sometimes cause RF noise in the receiver because of their 
very "hard" switching characteristic.

> Also, I would like to replace the 6H6 for the same reason, but what
> diodes should I use?

You would have to use diodes with very high back 
resistance. When I did what you want to do in a Scott SLR-
F, I used 1N34s, but there may be better diodes today. This 
was in the 1960s.

> I know that these items are available but in the interest of saving
> money, I would like to do it myself. . . .

Easily done. Have at it.

Ken Gordon W7EKB